1. Field of the Invention
The present invention relates to vehicle driving support apparatuses for preventing a collision by performing an automatic braking intervention, independently from a brake operation by a driver, when there is a high possibility that a subject vehicle can collide with a target object such as a preceding vehicle.
2. Description of the Related Art
In recent years, there have been various proposals for a vehicle driving support apparatus configured to recognize out-of-vehicle information in front of a vehicle by using a millimeter wave radar, an infrared laser radar, a stereo camera, a monocular camera, or the like, and to execute cruise control for the vehicle based on the recognized out-of-vehicle information. As an example of such cruise control function, there is widely known a function of follow-up cruise control to follow a preceding vehicle when such a vehicle is detected (captured) in front of a subject vehicle. The follow-up cruise control has widely been in practical use as part of adaptive cruise control (ACC). In a typical use of the ACC, the follow-up cruise control is executed when a preceding vehicle is detected in front of the subject vehicle, and constant speed cruise control at a preset speed determined by the driver is executed if no preceding vehicle is detected. In addition, for a vehicle driving support apparatus of this kind, there have been various proposals for collision prevention control (so called pre-crash braking control) that performs an automatic braking intervention, independently from a brake operation by a driver, when there is a high possibility that a subject vehicle can collide with a target object such as a preceding vehicle. For example, Japanese Unexamined Patent Application Publication (JP-A) No. 2009-262701 discloses a technology that sets a braking intervention distance based on a relative relationship between a subject vehicle and a target object recognized in front of the subject vehicle based on environment of a road in front captured by a camera, and performs an automatic braking intervention when the relative distance between the subject vehicle and the target object is equal to or shorter than the braking intervention distance.
When a vehicle is stopped by the above-described collision prevention control through an automatic braking intervention, the driver of the vehicle is generally required to take a measure against secondary accidents such as secondary collision by a following vehicle.
However, typical collision prevention control often brings a vehicle to a sudden stop through automatic braking at a maximum legally permitted braking force. If such a sudden stop is performed, the driver of the vehicle may become upset and may develop difficulty in calmly taking a measure against the secondary accidents.